1. Field of the Invention
This invention relates to an analog-cum-digital video recording and reproducing device which can perform recording and reproduction of HDTV digital signals as well as recording and reproduction of VHS analog signals.
2. Discussion of the Related Art
Conventional video recording and reproduction devices present problems in that recording and reproducing devices for HDTV digital signals and VHS analog signals need to be supplied in separate sets due to the differences in processing the signals, and the two systems have no interchangeability, as the HDTV digital signals cannot be recorded on, or reproduced from, a VHS tape.
That is, a VCR of VHS or S-VHS type according to the present NTSC or PAL method for recording analog video signals has a recording bandwidth of 5 MHz in case of VHS and 7 MHz in case of S-VHS. Accordingly, the conventional VCR for recording and reproduction of analog signals includes, for meeting such a recording bandwidth, one pair of video heads for recording video signals in 5 MHz or 7 MHz, a record reproduction amplifier for amplifying analog video signals picked up at the heads, and a signal processing circuit for reproduction of the amplified signals. At this time, the relative speed of a head drum with a diameter of 62 mm, matched to the recording wavelength of the video signals, is 1800 rpm, i.e., 5.8 m/sec.
In the case of digital signals like HDTV signals, since the quantity of video signal information required for one image is at least two times that of analog signal information required for the same image, a longer period of recording time is required. The recording should be in a higher concentration than an analog method in order to match the amount of tape required for recording the digital signal information to the similar level required for the analog signal information.
Accordingly, the recording and reproduction device for digital video signals includes, for recording the signals, one pair of video heads for recording video signals over 15 MHz bandwidth, a record reproduction amplifier for amplifying digital video signals picked up at the video heads, and a signal processing circuit for processing the amplified signals. The speed of the head drum matched to the recording wavelength of the video signal is 3600 rpm, i.e., 11.6 m/sec for a drum of 62 mm diameter.
Therefore, when carrying out digital recording or reproduction of one channel with the heads, since the recording or reproduction frequency bandwidth the head should take care of is 30 Mbps, i.e., about 15 MHz if it is digital data, the digital recording and reproduction requires high-performance heads as well as a relative speed between the head drum and the tape of more than 10 m/sec, which results in difficulty of running control.
Moreover, the recording and reproduction system for recording and reproduction of such digital video signals (in some cases, digital signals containing audio signals) presents a problem in that the system has no interchangeability with the VHS method of recording and reproduction of analog video signals (in some cases, analog signals containing audio signals).